Starting device for internal combustion engines



Sept. 18, 1951 PALFl I 2,568,359

STARTING DEVICE FOR INTERNAL-COMBUSTION ENGINES Filed 001". 24, 1949 4 Sheets-Sheet 1 Sept. 18, 1951 J. PALFl STARTING DEVICE FOR INTERNAL-COMBUSTION ENGINES Filed Oct. 24, 1949 4 Sheets-Sheet 2 Patented Sept. 18, I951 ""2",5tt,a59 sflitrhteanivice refinement- COMBUSTION i "ENGINES ,o 41 i This invention cdncerns-starting-devices' for internal'combustion engines of the kind ieo'mriiourrted coaxially with the"engine*'shaft arid-in driving connection therewith; By *pulling "the Itis an "oh-j e'ct' of the present invention to provide a 'constrnetionof ianli'starter which is" comp'act and robust "and which is autoir'iatieally disenga'geable frbrn' the engine shaft on'whieh "it'is mounted both when the engine'starts or"when is runs hackwa'riis after a mis fire.

It' isanother object 'of the-invention to "provide fa construction of pull=startr which isparticul'arly, althoughnotekelusively; applicabletosmail horse mower engines of the kindfrequently emplayed for drivineehain'saws" or outboardboat propulsion units.

Another obse'e't "of the invention isthe provision f a pull starter which isr'eadily detachable for inspection and servicing purposes" and which can be easily remountecl on the engine.

With these and 'dther bbjefets in v'iew' -the in vention consists essentially in the p'rovision; in

-a"*bull=starter;"of a -disen'gag'ealqle clriving' eonneetioh betweenth drum *and' the engine shaft'in cdrnbi-hationiwith ut'oinatic remand retraction ineehanism-f 'r engaging (fir disengaging the said 'tern 'sprinewh n istpratite tqlrewind-the cdid or tape" after each starting operation;

- In order-that the mten'tio'n-maybe more clearly understood; alternative construetions in accord- *a'nce therewith will 'now' be described; by "way "of example only, with reference to the eehonibanyme drawings in which-= Fig. 1 is an enpleded viem-in atrial "crosssection, of a preferred construction of a pull starter Fig. 2 is an axial section showine'the-parts'bf- Fig; 1 assembled and with the dogs in engagement during a sta'rting operation; N

Fig. 3- isanunderplan' of the'-pull*starter assembly;

Fig: 4-is-anend-view of the engineshaft', or

Figs; 6-8 are fregrrientary-'axial sections, on"

ilohalnn rain,

a 3 324, 194 2;, is'fiiiai nez-"izsisi vermin 061761591 5,1948

a" larger scale showing the 'parts' in i'suecessive relative positions .withthe "enacting; does seen in elevation for clarity of representation, and v Figsh9 and 10 illustrate; two alternative "con- "structions' of null starter "according" to the "invention; v

Throughout the drawings," like parts carry 'sirnila rreferencenumerals. a Tn thecon's'tr'uctidn illustrated in 'Figs. 1-8 the starter mechanism isjrnourited in an inverted dishedzliousin'gl which-is supported 'bympi'llar bolts "2 on the engine easing 'or'e'fr'ame 3. ,The engine crankshaft, or a'n;extens'ion' thereof," is indicatedat 4 (Fi s-1 and x2) andterminates withinthe starterhou'sing'i in a pulley 5 which eanbe used: as an emergency drumior a pull cord-or'tapein theevent of;failure of the starter Mechanism. This: "pulley 5' is hollow andphasia dog plate 6" of rectangular shape secured 1 thereto. The -dogp1ate*f 6 is recessed 'into theoutel: 'face of the pulley '5 andxis-loeated centrally .With respect to the axisof'theieng'inshaft libyomeans *ofalocatingring 1 riveted ati8'jto the'plate'fi (Fig-$4) the outerfrim' ofithentinalbeing' a snu 2r; -fit*within'*tlie"hollow 'pulley25 Thedog-platefi and locatingv ring l are held in .place. Joy-screws 9"whichare threaded intothewall of the shaft 4. Twotongues' I 0 are tb'ent'up' from the 'dog plate 6' to "cOn'stitute the di'iVen dogs "on the'engine Apair of drivingdogs -l I are,islidably mounted in sleeves [fl-held in theiboss l3 of a rotary d rnm assemblyeenerally indieatedmt I74 in Fig s,,l;and a rotary d a semb [Lcomprises a hollow annular spring'casing li aceornmodating a 'el'ock-type return f springi l6 having its inner end-ranchored'at L60; (Fig. 143) to the eja'sing fi whilst its outer end is anchored to, a stationary bearing ririg I], secured tp the starter hous ing l byscr'ews or rivets l8. The bearing ring J! has casing l5 is'freetorotatefthereomwithout axial displacement. An; annular deep-flanged pulley 2i! is secured'on the outer-surface of the spring re ins andgm th eronve ls jw abned. the hstalftingcordvzflrthe. freerendpi which terminates '55 in a "hand gripfl (M52). The arrangement is such that, when the cord 23 is pulled the pulley 22 is rotated and with it the casing I which carries round the driving dogs I I in their sleeves I2. The whole assembly I4 thus rotates about the axis of the engine shaft 4.

Within an axial bore through the boss I3 slides a cam feed nut 25 (see in particular Fig. 5) having a four-start quick pitch cam thread 23 formed therethrough. Adjacent its inner end, the cam feed nut 25 has two radial bores 21 (Fig, 5) formed at diametrically opposite points through the wall thereof. In each bore is secured apin 28 which projects outwards through a slot 29 in the adjacent wall of a respective sleeve I2 to engage in a similar bore 30 in the corresponding driving dog II. The nut 25 and the two driving dogs I I are thus constrained to move axially in unison. At a convenient point below the level of the bores 21, a recess 3I is formed in the internal wall of the cam feed nut 25. Into thisrecess is inserted a spring ring 32 which acts as a stop for .the nut in a manner described below.

Through the nut passes a reaction spindle 33 having a conical tip 34 at its one end and being reduced in diameter at its other end 35 .to form a spigot projecting through a cover 36 riveted to the housing I. Between the main body portion of the spindle 33 and the reduced diameter spigot part 35 is a squared portion 31 which engages in a correspondingly squared hole in a friction brake disc 38 located within the cover 36. On the side adjacent the housing I, the friction disc 38 carries a friction lining 39, and a helical compression spring 40 is mounted between the cover 36 and the friction disc 38 to urge the friction lining 39 into contact with the surface of the housing I. A similar and smaller compression spring 4| is mounted within the spring 40 between an abutment collar 42 on the spigot part 35 of the spindle 33 and the opposed surface of the friction disc to urge the spindle 33 outwards through the cover 36. This action maintains a transverse pin 43 secured in the spindle 33 adjacent the base of the conical head 34 in engagement with the inner end surface of the cam feed nut 25.

In use, the housing I is roughly aligned with the engine shaft 4 and feet Ia spaced around the rim thereof are engaged over the pillar bolts 2 to rest on platform nuts 44 screwed thereon. The latter are then adjusted to ensure parallelism between the axes of the drum assembly I4 and the engine shaft 4. To ensure coincidence of these axes, the spigot portion 35 of the spindle 33 is manually depressed to force the conical head 34 into a hole 45 in the centre ofthe dog plate 2 (see Fig. 6, dotted line position). When the starter mechanism has thus been correctly aligned, nuts 46 are tightened on the bolts 2 to clamp the feet Ia of the housing I on to the plat-.

form nuts .44. The latter may be locked on the bolts 2 by means of grub screws such as 4! (Figs. 1- and 2) The starter is then read for use, the parts being in the positions shown in Fig. 6.

To start the engine, the hand grip 24 (Fig. 3) is pulled to unwind the cord 23 from the drum I5. The latter begins to rotate on the stationary bearing ring I'I, axial displacement being prevented by the engagement of the fiange I5a with the retaining ring 20. As the drum I5 rotates, the nut 25 rotates with it, being constrained to do so by the pins 28 which project radially outwards therefrom into the pawls I I. The spindle 33, however, is prevented from rotation by the engagement of the squared portion 31 with the 4 friction disc 38 whose friction lining is pressed by the spring 40 against the outer face of the housing I. At the same time, the spindle 33 is outwardly biased by the spring 4I so that the pin 43 bears against the inner end of the nut 25. Hence, as the nut rotates relatively to the spindle 33, the pin 43 enters the cam thread 26 in the nut, and the spindle moves axially outwards until the shoulder at the inner end of the square portion 3'! bears against the inner surface of the disc 38. Further travel of the spindle 33 is then opposed by the spring 49, and the nut 25 begins to move inwards by virtue of the reaction of the pin 43 on the flanks of the cam thread 26.

As the nut 25 moves axially inwards towards v the engine shaft 4, it carries the dogs II with it by reason of the connecting pins 28, and with continued movement these dogs become projected sufiiciently to engage the driven dogs In on the engine shaft (see Fig. 7). When this driving engagement occurs, the thrust between the dogs I0, II is sufficient to prevent any further forward feed of the dogs I I and hence of the nut 25. The reaction at the pin 43 as rotation of the drum I5 continues thus produces an axially outward thrust which is sufficient to overcome the pressure of the spring 49 and the disc 38 is moved outward to disengage the friction linin 39 from the housing I (Fig. 8). Frictional resistance to rotation of the shaft 33 is thereby removed, and the shaft, together with the disc 38, rotates freely with the drum I5. The friction torque of the disc 38 does not, therefore, oppose the pull of the cord 23 dur ing the starting operation.

Under certain fortuitous conditions, it would be possible, in the absence of any provision to the contrary, for the'driving dogs II to be fed forward far enough prior to their engagement with the driven dogs ID for their tips to foul the plate 6. This is prevented by the engagement of the pin 43 with the spring 32 in the nut 25, the recess 3I accommodating the spring being located so as to ensure that the pin 43 makes contact with the said spring before the driving dogs II are advanced too far.

When the driving dogs II engage the drive dogs I9 (see Fig. 7) no further axial movement thereof, and hence of the cam feed nut 25, takes place. Continued rotation of the casing I5 by the pulley 22, however, causes an outward thrust to be exerted on the pin 28 by the cam threads 26, and the spindle 33 is displaced axially until the shoulder at the base of the squared portion 31 engages the edges of the square aperture in the friction disc 38. Continued exertion of the outward thrust forces the friction lining 39 away from the housing I until the frictional torque is reduced to a value equal to the tangential component of thrust exerted on the pin 43 by the flanks of the cam thread 26 in the nut 25. Thereafter the pin 33 rotates with th casing I5, and the. cord 23 is relieved of the tension which would have been required to overcome. the full frictional torque of the lining 39 on the housing I under the pressure of the spring 40.

When the engine fires, the driven dogs I0 overrun the driving dogs I I, and the latter are forced axially outwards up the sloping backs of the driven dogs. This axial movement is accommodated by the clearance space between the back of the friction disc 38 and the inner face of the cover 36, the whole nut and spindle assembly 25, 33 moving with the dogs II in the boss I3 of the casing I5. This movement is shown commencing in Fig. 8 and completed in Fig. 2. When this ocassesses-c :fully retracted (Figu'fi) :If the engine backfires while it is beingistarted.

the. reverse rotation imparted to i-the-nut L25 .re-

leases "the thrust :of .the spindle 33 against .athe

underside of the .disc"38. The lining 39 them- :upon. instantly grips .the housing .I to lockizzthe spindle :33 sothat. the'nut .25 :runs up on the pin 43 .ito'rwithdraw' the .dogs. I I iout of ;engagement .Withiethe drivenzdogs IiL. Theunecessarymaxial thrustto overcome :the;friction;,betweerrrthe;two .1 setsrof dogs is provided .rpartly i by -.:the outward :th-rust of the springy ll .onnthe spindle 33 and partly by the momentarily highgvaluexof ,ifric- 'fiOIl between the spindle flats .31 :andcthe edges of the-square hole :through the :friction disc--38,

.owing-lto itherapid reverse-acceleration of ,the

engine shaft.

lt -will thus beseen that themechanism is self-protecting against damage due to backfire,

- and-.can accordingly be of relatively light construction. Moreover, the assembly :is easily; detachable from the engine by releasingth'e nut;4.fi without disturbing the adjustment'of the platformznuts 44, so that inspection and servicing may readily, be effected with'a minimum of idle time ofuthe engine.

In both the alternativeforms of the invention shown in Figs. 9 and 10, the startermechanism iszmounted in an open housing ,I .bolted'torthe .engine frame or casing; 3 around the projecting .end .ofthe engine crankshaft ior-an extension thereof. .starter housing I, with a flange -4a.-carryingla :numberof driven dog-clutchteeth Ill which project. outwards away fromthe engine. Beyond .this ring of teeth In the shaft-4' is extendedsto .formaplain journal bearing Abforthe pulley 2-2 This shaft 4 is provided; within the on which the starting tape I23, is .wound. This pulley 22is free to rotate and toslide axiallyon thejournal bearing4b and is provided, on the ,fiange22a thereof which. faces towards the engine, with a number of driving dog clutch teeth II corresponding to .thenumber of the teeth "III on. theshaft 4. The pulley .22 hasan extension on its outer side in the form of a boss. 22b around which is wrapped a coil return. springjlfi ihaving its'outer end anchored to the wall'o'ffa cupt'IIE'. which is fixed within the .h'ousing 'l. The pulley 22 and itsboss 22?) together withf'the parts attached thereto, constitute the rotary drum of the starter, and the'return-spring I6 'is'operative to rotate the drum in-the-sense'for winding on-the starting tape I23, and-is also op- -erative to bias the drum in the axial direction to-separate the driving and 'drivendog clutch teeth I I, I ll respectively.

The boss 22b surroundsashort stub spindle .33 which is also located in the'starter housingd coaxially'with the drum. The inner end of this stub-spindle '33 is provided with a short cam head [25 m the circumferential face of 'which are formed two quick-pitch cam groovesl26r These cam'grooves are of a size to be engaged by a pair of diametrically opposed' feed pins I43 i which project radiallyinwards from the.boss 22b1and constitute axial feed members therefor:

rotated;with=..the drum ;.and;ithe engine shaft {4 m the :form:' of: starter illustrated :m ;r"1g.-:9,

when th'e partsareat rest 1(as shown). the: feed pins =:I 43 rest "against :the .5 outer .edge of the cam headil 25 on the stubi spindle:33.. Theoutenend of "'the=-latter projects'through the endwall;of th'elhousing .I .and :iS :providedgloeyondv a :ashoulder withi a: reduced squared. portion. 31 which. engages-with a correspondinglyisquared hole Lima frictionz jdisc .38 bearing againstthe outer: surface ofithechousingd. The-squared section 3".0f113h6 spindle-:33 -;is ..of a..length sufficient to .allow, .ior small iaxial, movement thereof relatively to. the frictionrdisc SB: .Beyond thissquared portion 31.

theistub SDI-[DQ113533 .115 reduced indiameterto terminate ina. screw;:thr.eaded .extension I 35 .which accommodatesaepair'of lock nuts :.I.42 .which;ser-ve .asean adj.ustable.abutment for raw. short-.0011 com.-

pression gspring :4! :surrounding the .reduced end .of-rthe spindle. .The, inner .end .of this spring bearsgonjgthe outer-end surfaceof a dished :cover 53.6 secured; to thewstartenhousing I and .enclosinggthe .friction. disc 38, the spring 4| -tending. to

:pullithe stub-spindle 33 :outwardsv and so to hold the cam head I25 thereon in contact withthe feed. pins, I43.- Within this .-,cover-36 is located the coilcompression spring .40 ,one endxof which .bearsaeainst the friction disc '38 whilst theother bears. against the inner: end: surface .01. the

cover-36;

the: fiexibletape I23 -.-is .pulled-zto rotate the pulley :Inpperatmn, when :the engine is ;to .be started,

22, and as the drum..22,-,22blbegins to rotate, the diametrically opposed pins I43 enter the quick- .pitch .cam grooves I28 .in-the. head I25. under .the influence. of: thespring '14 I.. :is-,free.-to move axiallywith. respect to the fric- The spindle. 33

tion .disc ,38 suificiently to .ensure the proper f en- ;gagement of the feed pins I43 with the cam grooves I26. .221) thuscausesthe. pins I43 to rundown the .quick-pitch .cam, the torsional. reaction on the stub spindle.33.during. this movement beingtaken -.by;-the.friction disc 38 .whichensures that. the .stub spindle 33 :is sufficiently firmly-held against ro- .tation. Consequently. the'drum .22, 22b is disiplaoed axially to..,br.ing..its .dog clutch .teeth ,II

Further rotationv of the; drum -.22.

into engagement with. the ,coactingdriventeeth lflonthe vengineshaft 4; Furtherpulling of the starting. tape ,I 23 thuscausesrotationof the engine shaft to effect starting of the engine.

=When the dog. clutch teeth I0, I I are .fully .en-

.gaged,.no.further axial. displacement of the drum 22,; 22b..can take .place,.and there is developed betweenithefeed pins-I43 and the outer.flanks of; the quick-pitch camgroovesIZG an axial thrust which tends to force thespindle 33 outwards. The

spindle islso proportionedthat when. this occurs then-shoulder at the .innerend of the squared section,31 engagesthefriction disc.38 around the square: hole therein *and- 2136111218 to. lift it against its compression :loading spring .40 out of engagement with the: surface ofthe. starter housing I.

By so doing, the:frictionwhich tends to prevent the .-rotation .of .the stubspindle 33 is substantially reduced. and :an: equilibrium =condition. is

set-' -up11-between the: thrust 'on the iquick pjitch .camzgrooves: I26 derived-1 .fromithe dra zzexerted rby the :friction disc 38 and thepressure of "the loadings spring 4.401.011 the' :frietion. 1 disc; Under these -;conditions;. the EStl'lba shaft 331can thusybe .withoutzexeessive dragzibeing transmitted to ;-the starting tape I 2 3 :;'during;:; the engine .1 starting :per-iodi. 752'.

while thfeadnum' 22 ,i22bis thus ;rotated-.;to: start 7 the engine, thespiral return spring I6 is wound up. to provide the necessary energy for rewinding the starting tape when the latter is released.

The spring I6 is also distorted axially and thus exerts an outward axial thrust on the drum tending to disengage the dogs I0, I I. This thrust is small compared with the friction between the dogs Ill, II and is not sufiicient to cause disengagement thereof during the starting period.

If the engine fires correctly, and before the flexible tape I23 is released, the dog clutch teeth I on the shaft 4 overrun the dog clutch teeth II on the drum. The back faces of these teeth are chamfered off so that the teeth II ride up on the teeth I6 and the drum 22, 22b is thrown out of engagement, the spindle 33 and friction disc 38 moving axially therewith as a unit against the compression loading spring 40. Immediately the tape I23 is released, the coil spring rotates the drum and, since the spindle 33 is, in the intervals between the engagement of the dogs Ii], I I intermittently held by its friction disc 38 against rotation, the pins I43 on the drum run back up the cam grooves I26 so that the spindle 33 and drum 22, 22b move axially towards each other until the dog teeth I6, II are completely disengaged and the pins I43 in the drum have passed out of engagement with the cam grooves I26. The coil spring I6 is then free to complete the rewinding of the starting tape I23 and the parts are thus returned to their original positions ready for the next starting operation.

Should the engine misfire and start to run back,

the drum 22, 22b is jerked back against the starting pull and begins to rotate in the opposite direction, This reverses the direction of the axial thrust exerted by the feed pins I43 on the cam grooves I26 so that the stub spindle 33, which is initially held stationary by inertia, moves axially inwards for a sufficient distance to allow the friction disc 38 tore-engage fully, under the action of its loading spring 40, the outer surface of the housing I and to hold the spindle 33 against rotation. Further backward rotation of the drum thus causes the pins I43 to run up the cam grooves I26 and throw the dogs I6, II out of engagement. The starting tape I23 can then be released to be wound on the pulley 22 by the spiral spring I6 and the parts are ready for the next operation.

In the alternative construction of Fig. 10, the feed pins I43 remain at all times in engagement with closed ended quick-pitch cam grooves I26a in the cam head I25 of the stub spindle 33. The outer end of the spindle 33 is squared at 31a to receive a double-sided friction disc I38 which is firmly locked on the spindle 33. The discI38 is enclosed by a flat cover plate I36 the inner surface of which is just clear of the outer surface of the friction disc I38 when the latter is in frictional engagement with the co-acting surface on the housing I. When there is no axial thrust in either direction on the spindle 33, the friction disc I38 is free to run between the opposed surfaces on the housing I and on the cover plate I36. So long, however, as the drum 22, 22b is being rotated relatively to the stub spindle 33 the engagement of the pins I43 in the cam grooves I26a maintains a resultant axial thrust on the stub spindle 33 in one or other direction, and the friction disc I38 is consequently held against the respective surface to oppose rotation of the stub spindle 33.

The dog clutch teeth ID on the engine shaft are mounted on a sleeve 48 which is keyed to the shaft 4 so as to rotate therewith but which can slide axially thereon against the thrust of a compression spring 49 which urges the dogs I0 towards the drum 22, 22b.

In the operation of this construction, the initial pull on the tape I23 causes the feed pins I43 to exert an outward axial thrust on the outward walls of the cam grooves I26a. The inertia of the stub spindle assembly initially tends to hold it against rotation with the pins I43 so that it is moved axially outwards to cause the friction disc I38 to engage the inner surface of the cover plate I36. Thereafter the spindle 33 is fractionally held against rotation by the friction disc I 38, and continued rotation of the drum 22, 22b causes the pins I43 to run down the quick-pitch cam grooves I26a so as to bring the dogs II on the drum into engagement with the dogs II) on the sleeve 48.

When the dogs II], II are fully engaged, the feed pins I43 reach the ends of the cam grooves I26a and there is no further axial thrust exerted on the spindle 33 to maintain the friction disc I38 in frictional engagement with the inner surface of the cover plate I36. The resistance of the spindle 33 to rotation is thus substantially reduced, and further pulling of the starter tape I23 causes rotation of the drum 22, 22b without any noticeable drag being exerted thereon by the friction disc I38.

If the engine fires correctly the dogs I0 on the sleeve 48 are thrown out of engagement with the dogs I I on the drum 22, 221) as the sleeve 48 moves axially towards the engine against the pressure of its engagement spring 49. Release of the tape I23 thus enables the drum 22, 22b to be rewound by its spiral spring I6 and the parts return to their initial position ready for the next starting operation.

If the engine misfires, the drum 22, 22b tends to be rotated backwards to rewind the tape I23 and the feed pins I43 immediately bear on the inward walls of the cam grooves I26a so that an axially inward thrust is exerted on the stub spindle 33. The friction disc I38 is thus brought into sufficiently tight engagement with the outer surface of the housing I to check the stub spindle 33 against rotation and the feed pins I43 run up the cam grooves I26a to pull the dogs II on the drum 22, 221) out of engagement with the dogs I 6 on the sleeve 48. The parts are thus returned to their initial positions ready for the next starting operation.

The frictional surface area may be increased if necessary by the substitution of a multi-plate clutch for the single friction disc 38 or I38 described above and the forces operating this clutch can be increased by decreasing the pitch angle of the cam threads or grooves 26, I26, I26a respectively.

with the drum and positively connected to the driving clutch component and the other having limited freedom of axial displacement under the influence of the axial component of reaction be- "tween the feed elements during a starting operation, and friction means for restraining rotation of the said other feed element relative to a fixed part of the mechanism for effecting axial feed displacement of the driving clutch component on rotation of the drum.

2. A pull starter for internal combustion engines having a casing, an axially engageable and disengageable driving connection between the drum and the engine shaft, co-operating relatively rotatable cam feed elements for effecting axial engagement and disengagement of the said connection on rotation of the drum in the starting and the reverse direction respectively, a frictional torque reaction member operatively associated with one cam feed element for yieldable engagement with the casing, the said one cam feed element being displaceable at a predetermined value of axial reaction between the cam feed elements for automatically disengaging the friction member from the casing when the driving connection between the drum and engine shaft is fully engaged 3. A pull starter for internal combustion engines comprising a drum, a spindle mounted coaxially with the drum, co-operating cam and follower elements on the spindle and the drum respectively, a frictional torque reaction member slidably but non-rotatably connected to the spindle, spring means for biasing the torque reaction member into frictional engagement with a fixed surface on the starter frame, and an abutment on the spindle for axial engagement with the friction member in the sense for opposing the spring bias under the influence of the axial reaction between the cam and follower members during a starting operation.

4. A pull starter for an internal combustion engine comprising a housing, a drum journalled in the said housing coaxially with the engine shaft for rotation without axial displacement, a tension element Wound on the drum for effecting driving rotation thereof, a driving clutch component mounted on the drum for sliding displacement relative thereto in the axial direction, a coacting driven clutch component on the engine shaft, and co-operating cam and follower feed elements the one slidably but non-rotatably received coaxially within the drum and positively connected to the driving clutch component and friction means for restraining rotation of the other feed element relative to a fixed part of the frame.

5. A pull starter as claimed in claim 1 comprising a spindle mounted coaxially with the drum,

co-operating cam and follower elements on the spindle and the drum, a friction member slidably but non-rotatably connected to the spindle, spring means for biasing the friction member into frictional engagement with a fixed surface on the mechanism, and an abutment on the spindle for axial engagement with the friction member in the sense for opposing the spring bias.

6. A pull starter as claimed in claim 4 wherein the frictionally restrained feed element comprises a spindle extending coaxially through the drum and a friction member slidably but nonrotatably engaged therewith, spring means for urging the friction member into engagement with a fixed surface on the housing, and a stop formation on the spindle for engagement with the friction member in the opposite sense during a clutch-engaging feed operation.

7. A pull starter as claimed in claim 6 including a spiral return spring mounted within the drum for rotating it in the direction opposite to the direction of rotation of the engine shaft on release of the tension element.

8. A pull starter for internal combustion engines comprising a housing embracing the free end of the engine shaft, a drum slidably journailed on the said shaft end and having the tension element wound thereon, axially engageable and disengageable driving and. driven clutch components rigidly secured on the drum and on the engine shaft respectively, and co-operating cam and follower feed elements the one mounted on the drum and the other having limited freedom of axial displacement under the influence of the axial component of reaction between the feed elements during a starting operation, and friction means for restraining rotation of the said other feed element relative to a fixed frame part for effecting axial displacement of the drum in the direction for engaging the clutch components on rotation thereof by the tension element and in the direction for disengaging the clutch components on reverse rotation of the drum.

9. A pull starter as claimed in claim 8 wherein the frictionally restrained feed element comprises a spindle located coaxially within the drum, a friction member slidably but non-rotatably engaged with the spindle, spring means for urging the friction member into frictional contact with a fixed surface, and abutment means on the spindle for limiting the freedom of relative sliding movement thereof with respect to the friction member in the direction for moving the said member out of contact with the fixed surface.

10. A pull starter as claimed in claim 8 wherein the frictionally restrained feed element comprises a spindle located coaxially within the drum, a friction member rigidly secured thereon, and opposed coacting fixed surfaces located with clearance on opposite sides of the friction member, in combination with a stop formation at each end of the cam surface on the said feed element to positively limit the amount of axial feed displacement of the drum.

JOI-IANN PALFI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,789,423 Benson Jan. 20, 1931 2,374,685 Kissel et a1 May 1, 1945 

